2. I beleive if you use blackra1n you shouldn't lose anything but there are always exceptions to the rule. Once I tried to do it for a friend and while updating to 3.1.2 the phone gave me an error. This caused me to put it into DFU mode and upgrade to 3.1.2 which wiped everything. However if you've backed up and synced at home if that did happen you would get everything back once you're home. Actually now that I think about it if you're going to connect the phone to your laptop do the backup of the phone on the laptop, just be sure to uncheck everything in each tab for music, videos, contacts, etc so that since you haven't sync'd with the laptop you wont wipe all the data by doing a sync. Then in the left column of iTunes right click on the phone and choose backup. Wait for someone to corroborate this since I've never backed up my phone on a second machine I don't know the implications.

3. Yes once you get home you can do a restore which will remove the JB/UL but it will restore you to factory setting so it will wipe your phone and you will have to restore from your backups. So why not just leave it JB/UL, it will not harm you, until the next firmware update which once applied will remove the JB/UL and you shouldn't lose your data during the process.

If you're going to do the process with blackra1n be sure you put your phone in Airplane mode before you start the process and when you plug in your phone to the USB cable make sure if iTunes starts automatically you close it before running blackra1n.